theme_toggle
The ThemeToggle widget is a custom and fancy toggle switch for Themes. You can use custom emoji for on(Dark) and off(light).
Previews
Rotating Toggle button

Just give rotation as true then the emoji rotate on the toggle click.
ThemeToggle(
iconOffSize: 30,
iconOnSize: 30,
rotation: true,
onChanged: (bool change) {
setState(() {
change = !change;
change ? theme = 'Dark' : theme = 'Light';
});
},
)
Fading Toggle button

Just give rotation as false then it changes to fade animation.
ThemeToggle(
iconOffSize: 30,
iconOnSize: 30,
rotation: false,
onChanged: (bool change) {
setState(() {
change = !change;
change ? theme = 'Dark' : theme = 'Light';
});
},
)